The present invention relates to the field of data management in optical systems, and more particularly, to a method and system for data management in DVD (Digital Video Disc) systems.
In optical systems, host computers are typically connected to an optical medium by an interface and a data management system. For example, in a DVD system, the host is connected to a DVD disc via an Advanced Technology Attachment Packet Interface (ATAPI) interface and a DVD interface circuit. A DVD interface circuit typically contains a microprocessor, a buffer, an embedded controller and memory for storing computer programs which run on the controller and the microprocessor. The host could be a personal computer or any other computing platform that is capable of communicating with the ATAPI interface.
When a host issues a request for DVD data, the request is transferred to the DVD interface circuit through the ATAPI interface. The DVD interface circuit processes the request by retrieving the requested data from a DVD disc and transferring the retrieved data to the host through the ATAPI interface. During this process, each component within the DVD interface circuit has tasks to perform. Efficient task allocation and task automation are important design goals for DVD interface circuits. For example, if more tasks are allocated to the embedded controller, less work is demanded of the microprocessor and vice versa. Task automation can be achieved by creating programs which place more reliance on the controller chip than the microprocessor.
Because DVD systems are new to the field of optical system technologies, existing DVD systems typically implement audio CD (Compact Disc) system technologies. CD technologies are not suitable for DVD systems because of the many fundamental differences between CD and DVD data storage structure. Data is stored on CD and DVD discs by data blocks. On CD discs, each data block is a sector of approximately 2K bytes with a corresponding ECC (Error Correction Code) protection per block. Each CD data block is identified by an unique ID. Like CD data blocks, each DVD data block on a DVD disc has an unique ID. In contrast to CD data blocks, however, each DVD data block typically has 16 data sectors of approximately 2K bytes each. Each DVD data block of approximately 32K bytes has only one corresponding ECC protection. Since all 16 sectors of a DVD data block are protected by a common ECC, a DVD data block is sometimes referred to as an ECC Block.
Regardless of the optical media, most hosts read data in units of 2K bytes. In a DVD system, if a host wants to read a single 2K byte sector on a DVD disc, typically, at least one entire data block of approximately 32K bytes needs to be retrieved so that the desired sector can be found and transferred. This large amount of data retrieval makes data management much more difficult in DVD systems than in CD systems. As will be seen below, data management schemes used in CD systems are simply inadequate for DVD systems.
In CD systems, when a host issues a request for CD data, the microprocessor within the CD data management circuit begins to locate a target data sector on a CD disc in response to the request. During the process to locate the target sector, the microprocessor compares every data sector ID retrieved by the controller to the target data ID until the target ID for the target data sector is found. When the target ID is located, the microprocessor switches the controller from a xe2x80x9cmonitoringxe2x80x9d mode to a xe2x80x9cbufferingxe2x80x9d mode so that the controller can begin to buffer data sectors into a data buffer. During the buffering process, the controller continues to buffer data sectors until the microprocessor realizes that enough sectors have been transferred and instructs the controller to stop.
In CD systems, most error checks are performed as data sectors are being stored into a data buffer. Data sectors are generally stored at predetermined locations in the data buffer. Before any CD data is transferred from the buffer to a host, typically, the microprocessor performs a final check by looking in the auxiliary portions corresponding to each data sector in the data buffer. Accessing the data buffer is a time consuming process. Error checking is relatively simple for CD data because each CD data block or sector is only 2K bytes in size.
CD systems rely heavily on the microprocessor and require multiple instructions from the microprocessor to the controller. These heightened demands on the microprocessor may cause delays in transferring of data sectors which may cause the system flow to crash. Any inefficiency in CD systems is exacerbated when the same data management technique is used in DVD systems. Due to the size of each data block in a DVD system, any retrieval of data block related information involves the retrieval of a large amount of information, causing, among other inefficiencies, further delays in data transferring.
In view of the foregoing, it would be highly desirable to provide a system that accommodates the differences in data structure between a CD and a DVD. Such a system should exploit techniques for efficient data management, preferably ones that allocate more tasks to an embedded controller than to the microprocessor.
This invention provides a method and system for allocating task automation to the embedded controller in a DVD interface circuit. Task automation in the controller is achieved by improvements in the controller hardware and the computer program which provides instructions to the controller.
The controller includes circuits and preprogrammed registers to automatically locate and transfer the requested data blocks. A comparator circuit in the controller compares any retrieved data block IDs to a target data block ID until the target data block is located. A monitoring circuit in the controller monitors the number of data blocks transferred to a data buffer to ensure that the controller automatically stops transferring data blocks when all of the requested data blocks have been transferred.
In this invention, the data buffer has a number of areas separated by preprogrammed automatic pointers. Each area defined by automatic pointers can locate anywhere in the data buffer. This automatic storage of portions of the data block in appropriate areas of the data buffer facilitates more efficient transfer of the data portion to the host by allowing uninterrupted data transfer.
Data blocks are corrected and checked in the data buffer for any error. The results of the error correction and checking are latched into a set of registers within the controller. Just prior to transfer of data to a host, the data status in the registers is checked. The registers are preprogrammed to automatically update the status of data check for each data block. Using registers in the controller to automatically monitor the status of data blocks reduces the burden on the microprocessor and increases efficiency.
This invention greatly increases controller task automation, reduces cost and improves efficiency of data transfer to a host.